The primary RTEMS source image is a collection of software that is licensed under a variety of free and open source licenses appropriate for use in embedded systems. A common characteristic of all of these licenses is that they allow linking with no source redistribution requirements placed on the end user application. The following licenses apply to the various components.

• Primary RTEMS License which covers most of the source code in RTEMS.
• Two-Clause BSD license. Completely new submissions are encouraged to use this license. See issue 3053 for information about relicensing RTEMS to this license.
• RTEMS Documentation License
• TCP/IP Stack License
• RPC/XDR License
• Stanford University Permissive License